Instances in WoW can be the bread and butter of the game. Sure you can level your character through exploration (all though that is pretty limited), killing mobs and questing, but once you hit end game you spend the majority of your time in dungeons. With this in mind the great people at Blizzard are going to bring us enhanced dungeon maps. The new maps are laden with great information regarding the bosses that will be encountered. We will have 3D models of the boss, lore as to why we are fighting them (you know, besides money and loot). You will also be told meta-game information such as what abilities that the bosses can use and what loot that the bosses will drop. This will be availble in both 5-man dungeons and raids.
Let us not forget too, that with patch 4.1.0 and Cataclysm a lot of the vanilla WoW dungeons are going to see a bit of a split up. Examples of this will be seen in the massive dungeons such as Black Rock Depths and Maraudon. Maraudon is going to be split into two different wings, a life area and an elemental area. Black Rock is getting teleporters to help you move around a bit better. We are also seeing Uldamon getting split into two sections. This will make lower level players able to get more done in less time. Looking foward to it when I start leveling some new toons.